Multi-mode envelope tracking amplifier circuit

Abstract

A multi-mode envelope tracking (ET) amplifier circuit is provided. The multi-mode ET amplifier circuit can operate in low-resource block (RB) mode and high-RB mode. The multi-mode ET amplifier circuit includes an ET amplifier(s) to amplify a radio frequency (RF) signal(s) to an amplified voltage, low-RB switcher circuitry to generate a direct current (DC) current, and high-RB switcher circuitry to generate an alternating current (AC) current. The amplified voltage, the DC current, and the AC current collectively cause the RF signal to be transmitted at a determined power. A control circuit(s) activates the high-RB switcher circuitry in the high-RB mode to provide the AC current, thus minimizing AC current sourced from the ET amplifier(s). As a result, it is possible to improve efficiency of the ET amplifier(s) and the multi-mode ET amplifier circuit in the high-RB mode and the low-RB mode.

What is claimed is: 
     
       1. A multi-mode envelope tracking (ET) amplifier circuit configured to operate in a low-resource block (RB) mode and a high-RB mode, comprising:
 a signal output coupled to a radio frequency (RF) transmission circuit for transmitting an RF signal at a determined power; 
 at least one ET amplifier comprising an amplifier input configured to receive the RF signal and an amplifier output coupled to the signal output, the at least one ET amplifier configured to amplify the RF signal to an amplified voltage at the amplifier output based on a supply voltage; 
 low-RB switcher circuitry configured to generate a direct current (DC) current; 
 high-RB switcher circuitry configured to generate an alternating current (AC) current; and 
 at least one control circuit configured to:
 activate the low-RB switcher circuitry in the low-RB mode and the high-RB mode to provide the DC current to the signal output; 
 activate the high-RB switcher circuitry in the high-RB mode to provide the AC current to the amplifier output; and 
 deactivate the high-RB switcher circuitry in the low-RB mode. 
 
 
     
     
       2. The multi-mode ET amplifier circuit of  claim 1 , wherein the at least one control circuit is configured to:
 activate the high-RB switcher circuitry in response to determining that the at least one ET amplifier is supplying the AC current; and 
 deactivate the high-RB switcher circuitry in response to determining that the at least one ET amplifier is sinking the AC current. 
 
     
     
       3. The multi-mode ET amplifier circuit of  claim 1 , wherein:
 in the low-RB mode, the RF signal comprises less than or equal to twenty-five RBs; and 
 in the high-RB mode, the RF signal comprises more than twenty-five RBs. 
 
     
     
       4. The multi-mode ET amplifier circuit of  claim 1 , wherein:
 the low-RB switcher circuitry comprises a first DC-DC converter and a first inductor having a first inductance; and 
 the high-RB switcher circuitry comprises a second DC-DC converter and a second inductor having a second inductance substantially smaller than the first inductance. 
 
     
     
       5. The multi-mode ET amplifier circuit of  claim 4 , further comprising an offset capacitor configured to:
 couple the amplifier output of the at least one ET amplifier to the signal output; 
 convert the amplified voltage at the amplifier output to an output voltage higher than the amplified voltage at the signal output; and 
 provide the AC current from the amplifier output to the signal output. 
 
     
     
       6. The multi-mode ET amplifier circuit of  claim 5 , wherein the at least one control circuit comprises:
 a low-RB control circuit coupled to the low-RB switcher circuitry and configured to activate the low-RB switcher circuitry in the low-RB mode and the high-RB mode; and 
 a high-RB control circuit coupled to the high-RB switcher circuitry and configured to activate the high-RB switcher circuitry in the high-RB mode and deactivate the high-RB switcher circuitry in the low-RB mode. 
 
     
     
       7. The multi-mode ET amplifier circuit of  claim 6 , wherein the low-RB control circuit and the high-RB control circuit are each provided as a bang-bang controller (BBC). 
     
     
       8. The multi-mode ET amplifier circuit of  claim 6 , wherein the low-RB control circuit is provided as a pulse-width modulation (PWM) controller. 
     
     
       9. The multi-mode ET amplifier circuit of  claim 6 , wherein the output voltage, the DC current, and the AC current are configured to cause the RF signal to be transmitted at the determined power from the signal output. 
     
     
       10. The multi-mode ET amplifier circuit of  claim 9 , wherein the at least one ET amplifier is further configured to:
 provide a supplemental AC current to the signal output when the AC current is insufficient to cause the RF signal to be transmitted at the determined power from the signal output; and 
 sink a portion of the AC current when the AC current is excessive to cause the RF signal to be transmitted at the determined power from the signal output. 
 
     
     
       11. The multi-mode ET amplifier circuit of  claim 10 , wherein:
 the high-RB switcher circuitry is further configured to generate a switcher sense current in proportion to the AC current generated by the high-RB switcher circuitry; and 
 the at least one ET amplifier is further configured to generate an amplifier sense current in proportion to the supplemental AC current generated by the at least one ET amplifier, wherein:
 the amplifier sense current is a positive current when the at least one ET amplifier is providing the supplemental AC current; and 
 the amplifier sense current is a negative current when the at least one ET amplifier is sinking the portion of the AC current. 
 
 
     
     
       12. The multi-mode ET amplifier circuit of  claim 11 , wherein the high-RB control circuit is further configured to:
 receive the amplifier sense current from the at least one ET amplifier; 
 control the high-RB switcher circuitry to increase the AC current in response to the amplifier sense current being the positive current; and 
 control the high-RB switcher circuitry to reduce the AC current in response to the amplifier sense current being the negative current. 
 
     
     
       13. The multi-mode ET amplifier circuit of  claim 11 , wherein the low-RB control circuit is further configured to:
 receive the amplifier sense current from the at least one ET amplifier; 
 receive the switcher sense current from the high-RB switcher circuitry; and 
 control the low-RB switcher circuitry to adjust the DC current based on the switcher sense current and the amplifier sense current. 
 
     
     
       14. The multi-mode ET amplifier circuit of  claim 13 , further comprising:
 a current combiner configured to receive and combine the amplifier sense current and the switcher sense current to generate a combined sense current; and 
 a gain regulator configured to:
 receive the combined sense current from the current combiner; 
 scale the combined sense current based on a scaling factor to generate a scaled sense current; and 
 provide the scaled sense current to the low-RB control circuit; 
 
 wherein the low-RB control circuit is further configured to control the low-RB switcher circuitry based on the scaled sense current. 
 
     
     
       15. The multi-mode ET amplifier circuit of  claim 14 , wherein the scaling factor is equal to one in the low-RB mode and is equal to less than one in the high-RB mode. 
     
     
       16. The multi-mode ET amplifier circuit of  claim 14 , wherein the scaling factor is determined in relation to the first inductance of the first inductor and/or the DC current generated by the low-RB switcher circuitry. 
     
     
       17. The multi-mode ET amplifier circuit of  claim 11 , wherein the low-RB control circuit is further configured to:
 monitor the output voltage at the signal output to determine whether the output voltage is sufficient to cause the RF signal to be transmitted at the determined power from the signal output; and 
 control the low-RB switcher circuitry to increase the DC current when the output voltage is insufficient to cause the RF signal to be transmitted at the determined power from the signal output. 
 
     
     
       18. The multi-mode ET amplifier circuit of  claim 11 , further comprising delay compensation circuitry coupled to the at least one ET amplifier and the high-RB control circuit, the delay compensation circuitry configured to delay the RF signal to compensate for a processing delay associated with the high-RB switcher circuitry in the high-RB mode. 
     
     
       19. The multi-mode ET amplifier circuit of  claim 18 , wherein:
 the delay compensation circuitry is further configured to generate a differential current indicative of an estimated current change at a determined time; and 
 the high-RB control circuit is further configured to control the high-RB switcher circuitry based on the differential current. 
 
     
     
       20. The multi-mode ET amplifier circuit of  claim 1 , wherein in the low-RB mode, the low-RB switcher circuitry is further configured to provide the AC current to the signal output. 
     
     
       21. The multi-mode ET amplifier circuit of  claim 1 , wherein in the high-RB mode, the high-RB switcher circuitry is further configured to operate based on the supply voltage of the at least one ET amplifier.